Process of dewaxing hydrocarbon oils



Patented Apr. 8, 1941 PROCESS OF DEWrziiLllg G HYDROCARBON Leo D. Jones, Philadelphia, Pa., assignor to The Sharples Corporation, Philadelphia,- Pa., a corporation of Delaware N 0 Drawing. Application December 2, 1938,

Serial No. 243,558

4 Claims.

The present invention pertains to the dewaxing of petroleum stocks and to diluents to be used in connection with such dewaxing operations. The invention pertains particularly to a process by which petroleum stock is diluted with solvents of high specific gravity, chilled to a temperature sufficiently low to precipitate the wax content of the stock and thereafter centrifuged. The diluents employed are of sufficiently high specific gravity andare blended with the petroleum stockin sufiiciently large proportions to produce, after chilling, an oil phase of very substantially higher specific gravity than the precipitated wax phase. As the result of this difference in specific gravity, the oil phase occupies the space adjacent the inner peripheral wall of the imperforate centrifugal rotor through which the mixture is passed to effect centrifugal separation of the precipitated Wax from the diluted oil phase.

Processes of this general character are described in the patent and technical literature. In this connection, attention is called to the United States Patent to Jones, 1,930,479, and Backlund, 1,676,069.

In the practice of dewaxing petroleum stocks by the process described in Backlund Patent 1,676,069, for example, an adequate separation of wax from oil can be obtained after blending with trichloro ethylene, provided the stock is chilled to a very low temperature such as 40 F. Such an operation is, however, relatively expensive because o-f the cost of equipment required to chill the stock to this low temperature, and the expense of the power required for the chilling operation. Trichloro ethylene is an excellent solvent for petroleum stock. but it is too good a solvent for the wax content of the stock, and the wax cannot therefore be precipitated from the stock to the extent necessary to produce lubricants of the low cold test now required in commerce, except by resort to chilling operations in which the stock is cooled to an unusually low point. In order to obviate this defect, trichloro ethylene has heretofore been blended with symmetrical dichloro ethane and other compounds, to cause precipitation of the wax at higher temperatures than when the trichloro ethylene is used alone. Experimentation has proved that, when trich'loro ethylene is blended with dichloro ethane in the proper proportion, which will vary with the individual petroleum stock to be dewaxed, the defect of unusually low chilling requirements inherent in the use of trichloroethylene alone can be avoided. A typical mixture of symmetrical dichloro ethane and trichloro ethylene which I dewaxing operations has also been suggested and operations.

mixtures of carbon tetrachloride and symmetrical dichloro ethane have been employed in such Carbon tetrachloride, when used alone or in substantial proportions in conjunction with symmetrical dichloro ethane, has the advantage that it affords a non-inflammable dewaxing diluent but it has the serious disadvantage that it is highly corrosive and its use is therefore undesirably destructive to metallic parts of the dewaxing apparatus.

The object of the present invention has been to afford a composition for the performance of dewaxing operations which is free of all of the objections discussed above with respect to the above-mentioned diluents.

The present invention rests upon the discovery that, when a mixture of symmetrical dichloro ethane with trichloro ethylene in proportions satisfactory for the production of low cold test oils at ordinary chilling temperatures is mixed with a relatively small proportion of dichloro methane, the resulting diluent can be used in the performance of dewaxing operations involving chilling to precipitate wax and separation of precipitated wax by centrifugation, gravity settling or filtration, with avoidance of all of the defects discussed above with respect to previously used diluents or diluent mixtures. When symmetrical dichloro ethane, or a mixture of symmetrical dichloro ethane with trichloro ethylene in proportions varying between '70 parts of symmetrical dichloro ethane to- 30 parts of triwithout the fire hazard entailed in connection with shipment, storage and use of the prior art diluents discussed above. I

While the invention has been described above with reference to symmetrical dichloro ethane;

it is to be understood that dichloro propane is the equivalent of symmetrical dichloro ethane in this connection and reference to symmetrical dichloro ethane in the attached claims istherefore to be construed'liberally as covering both of these compounds.

Modifications will be obvious to those skilled in the art, and I do not therefore wish to be limited except by the scope of the sub-joined claims.

I claim: 1. As a dewaxing diluent, a mixture containing symmetrical dichloro ethane and trichloro ethylene in a ratio adapted to cause precipitation of wax from petroleum stock without substantial precipitation of paramnic oil from said stock upon dilution and. chilling of said stock with the mixture, said mixture containing also a suiiicient proportion of dichloro methane to render the resulting mixture non-inflammable. 2. A process of dewaxing petroleum stocks comprising diluting the stock to be dewaxed with a mixture containing symmetrical dichloro ethane and trichloro ethylene in proportions adapted to cause precipitation of wax by chilling without precipitating a substantial amount of paraffinic oil, said mixture containing also sumcient dichloro methane to render it non-inflammable, chilling the diluted stock to effect precipitation of wax, and thereafter separating precipitated wax from the solution of oil in the mixture of diluents by Stratification under the influence of the specific gravity difference between the precipitated wax and diluted oil.

3. A process of dewaxing petroleum stocks comprising diluting the stock to be dewaxed with a mixture containing symmetrical dichloro ethane and trichloro ethylene in proportions adapted to cause precipitation of wax by chilling without a substantial amount of parafiinic oil, said mixture containing also approximately 12% of dichloro methane based on the quantity of the total mixture, chilling the diluted stock to effect precipitation of wax, and thereafter separating precipitated wax from the solution of oil in the mixture of diluents by stratification under the influence of the specific gravity difference between the precipitated wax and diluted oil.

4. A process of dewaxing petroleum stocks comprising diluting the stock to be dewaxed with a mixture containing symmetrical dichloro ethane and trichloro ethylene in the ratio of .approximately 7:3, said mixture containing also approximately 12% of dichloro methane based on the quantity of the total mixture, chilling the diluted stock to efiect precipitation of wax, and thereafter separating precipitated wax from the solution of oil in the mixture of diluents by Stratification under the influence of the specific gravity difference between the precipitated wax and diluted oil.

LEO D. JONES. 

